Clever Alchemist is a craftable set. When you drink a potion you feel a rush of energy, increasing your weapon and spell damage by 661 for 15 seconds.
The 661 spell and weapon damage can also be amplified by percentage modifiers like Major Sorcery/Brutality 20% increased spell or weapon damage. To activate the set you need to be in combat, otherwise you will not get any extra spell and weapon damage when you drink a potion.
Clever Alchemist is part of the Thieves Guild DLC. The crafting station is located in Hew’s Bane (No Shira Workshop). You can craft any armor, weapon or jewelry with this set in any motif style you know, as long as you have 7 traits researched (per item). You can trade crafted pieces to other players. Each set item becomes bound on equip.
Found in Hew's Bane
ESO
Sets